It’s worth pointing out that street fighting is just fighting, there’s nothing special associated with it and the idea that it’s unpredictable is… untrue. The true moral of Fight Club is that Fight Club is a stupid expression of toxic masculinity that is worth nothing. Getting beat up a lot doesn’t make you a better fighter. It will give you an endorphin high and sell you on the illusion of your own toughness.

Street fighting is extremely predictable, especially from self-taught fighters. This is because self-taught fighters have a limited move set. A move set that is limited to what they’ve seen in practice by someone else. Today, this means what you see on on television. Whether that’s professional boxing, UFC, WWE, or someone trying to ape the moves of a Hollywood action star like Bruce Lee, Jet Li, Jackie Chan, Chuck Norris, etc.

An untrained swordfighter is even more screwed than untrained hand to hand because sword combat on the street is called dueling and they practice that in the salle.

Your character would actually be more unpredictable via seeking out secondary instruction from “practical” aka practical application or more street minded sources. This can be police self-defense, training in forms like Krav Maga, and others that focus on teaching your character to use what they’ve learned in their studio out in the real world.

The techniques don’t change, but the mentality does.

For a character who has formal training, they’re going to re-learn to use what they already know in a new environment where the stakes are higher. The difference between a recreational martial art and a practical one is what you’re training for rather than the techniques themselves. Changing from one to the other involves changing how your perspective on your environment and learning to evaluate threats as opposed to simply focusing on technique and training for sport or spiritual enlightenment.

All martial arts training revolves around survival on some level.

For a character to “train” in “street fighting”, they’d have to go out and fight on the street. This would involve taking their life in their hands and risking it for… what, exactly? They saw value in going out to beat up/get beat up by random strangers at a bar, in a Fight Club style set up, or something similar to backyard wrestling rings.

This character isn’t actually learning a new fighting style. They’re taking what they know out into the real world to test it. (An act which will get you evicted from most martial arts studios if they catch you, especially if you’re a minor.)

The “unpredictability” of street fighters comes from the fact that most people can’t predict when a fight is about to break out. They don’t see it. They don’t get in the frame of mind for it. They see the aftermath, after the first punch is thrown, and are stuck mentally playing catch up as they’re getting pounded.

The average street fight lasts less than thirty seconds.

Those first few milliseconds at the beginning of a fight are crucial, as is your frame of mind before the first punch is thrown. Getting yourself into the right mindset, ready to defend, and ready to fight means that you’re not going to be blindsided when the time comes to go.

That is the unpredictability of street fighters, though. They’ve learned that the first one to the punch usually wins, they’ve learned that the most aggressive fighter is the successful one. So, they to take the initiative, blindside, and pound. By the time the other person mentally catches up, the fight’s over and they’re either broken on the ground or dead.

“Unpredictable” is just code for “I didn’t expect that”. It isn’t a mystical state that is forever surprising. Through time and experience, the unpredictable becomes predictable for the individual. For the same technique to continue being unpredictable, you need to consistently perform it on those who’ve never seen it before. The street fighter illusion will fall apart fairly quickly because, when you’re working from the basis of the self-taught, street fighting isn’t that complex.

Those with formal training benefit from not only their own experiences, but the experience of their instructors, their instructors’ instructors, and everything else that comes with a martial that has survived for multiple generations. It’s a battle against a multitude of experiences, against a co-operative effort.

I will point out again that combat is a science and utilizes science as a means to kill people. It isn’t part of human nature and natural instinct, it is specifically designed to exploit them.

Street fighting is fighting in an uncontrolled environment, where the risks are higher due to the lack of protections and harm is assured.